Spatial Variability in Eolian Dune and Interdune Morphology in the Rub'Al-Khali Dune Field, Saudi Arabia: Implications for Reservoir Prediction

Almasrahy, Mohammed A.; Mountney, Nigel

Significant lithological heterogeneities in eolian successions arise from the juxtaposition of dune elements with generally favorable reservoir properties against interdune elements that may act as baffles to flow. Prediction of the arrangement of such elements in subsurface successions is therefore important in developing eolian reservoir models, yet such predictions are difficult because the preserved thickness, continuity and internal facies composition of both dune and interdune elements vary spatially both locally and regionally. Important controls on spatial architectural variability include the morphology and migratory behavior of the original bedforms and their intervening interdunes at the time of accumulation.

The Rub'Al-Khali desert of Saudi Arabia is covered by the latest generation of public-release satellite imagery, which reveal a varied range of dune types, the morphology of which changes systematically from the dune-field center to its margins. Analysis of geomorphic relationships between dune and interdune sub-environments documents how the morphology, geometry, internal facies arrangement and relationship of the various depositional architectural elements produced by these geomorphic features vary over space from central to marginal settings. A series of quantitative approaches have been employed to characterize the complexity present in areas where large, morphologically complex and compound bedforms gradually give way to smaller, simpler bedform types at dune-field margins. Parameters describing bedform spacing, parent morphological type, style of subordinate bedform superimpositioning, bedform orientation, lee-slope expression, along-crest sinuosity and amplitude have each been recorded in a relational database, as have parameters describing interdune size (long and short axis dimensions), orientation, style of connectivity to neighboring interdunes, substrate condition (dry, damp, wet), and nature of any associated sedimentological processes. Results have been used to generate a series of synthetic 3-D stratigraphic architectural models with which to illustrate the range of possible sedimentological complexity expected for preserved eolian dune and interdune successions. This work has applied implications because interdune and dune-plinth elements typically act as principal and subordinate baffles to flow, respectively, in eolian hydrocarbon reservoirs, whereas dune lee-slope elements typically represent effective net reservoir.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013